affordable battery tester

I killed my first set of RV batteries relying on the idiot lights and voltage chart. X2 on the battery monitor counting amp-hours! My second set of (Costco) batteries is in excellent shape after five years.

Unfortunately none of our vehicles have battery monitors so I do use the voltage method for the engine batteries - very carefully. I disconnect the battery in the evening and check the voltage the next morning. I think the chart is fairly accurate that way. Although the RV batteries are still well over 12.7 volts after being disconnected for a month.

2oldman wrote:
For practical purposes (ours), they are good enough. Everybody knows not to rely on voltage during charging, under load, or too soon after charging or load.

You can rely on voltage, I can - together with the data on MPPT display and with what I know about my energy habits. It doesn't sound like the OP know/knew when and how they could rely on voltage.

They wanted a handheld device with accurate reading of SOC% - not just a handheld voltemer and tables. Never clarified their offfgrid scenario or when and how often they need SOC%.

2oldman wrote:
Everybody knows not to rely on voltage during charging, under load, or too soon after charging or load.

Wrong on two counts.

EVERYBODY doesn't know anything.

And most people experienced and trained in electronics will find voltage measurements under the conditions you mentioned very useful......IF you understand what it SHOULD be in those conditions.

For instance:
I watch the voltage during charging to be sure it IS charging and to see when I can discontinue the charging.

I watch the voltage during discharge to get an idea of when I need to reduce the load to extend the run time......or to know when to start charging.

And I watch the voltage immediately after charging (with minimal load) to see if it drops too fast.....which is an indication of a failing battery.

Almot wrote:

2oldman wrote:
So all these charts showing voltage and percentage of charge are, what.. nonsense?

Those tables are "approximate". Open-circuit tables make sense. The longer it had rested, the correct-er they become.
Under-load tables depend on the load.

Yes, they are, which I guess is my point. For practical purposes (ours), they are good enough. Everybody knows not to rely on voltage during charging, under load, or too soon after charging or load.

Yes, an ah meter like Trimetric is much better, but that wasn't the OP's question.

Cydog15 wrote:
Because it too dynamic and not accurate. Everybody knows that. Draw the DC down and it's not going to bounce back to real SOC.

No sorry, not true.

If you remove ALL of the load for about an hour, it absolutely WILL "bounce back" to a nominal resting voltage that corresponds very closely to it's "real" SOC.

Where exactly did you get that bit of mis-information ?
Everybody does NOT know that......mostly because it is not true.

2oldman wrote:
What's the problem with voltage? It's a common and reliable indication of remaining capacity on LA batteries. I would think a battery tester (not a hydrometer) would use voltage.

Because it too dynamic and not accurate. Everybody knows that. Draw the DC down and it's not going to bounce back to real SOC. I like the Trimetric.

2oldman wrote:

Almot wrote:
Voltmeter for SOC is like a broken clock that is right twice a day..

It's close enough.

These folks would tend to agree...

2oldman wrote:
So all these charts showing voltage and percentage of charge are, what.. nonsense?

Those tables are "approximate".
Open-circuit tables make sense. The longer it had rested, the correct-er they become.
Under-load tables depend on the load.

Tables during charging - I think you know the answer :)... The could be graphs for charging process, not simple tables like those linked above, and it depends on what battery and what charger. 3-stage charger may generate a graph different from the one by BFL13.

Almot wrote:

2oldman wrote:
It's close enough.

Marginally better than OEM panel with indicators Full/Empty for black tank and batteries..

So all these charts showing voltage and percentage of charge are, what.. nonsense?

10.5 volts can mean anything between near Full, and stone dead,...all depends on the load at the time.

In reality, once you are experienced at off grid camping, you won't have much use for battery monitoring. My living habits don't change, so its just routine, charging x amount of hrs per day, keeps it all going fine.
The exception to that would be if you have inconsistent solar charging, that could affect generator run time. But on full sun days, everything will be routine.